JP2020066015A - Laser processing method - Google Patents
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- 238000003672 processing method Methods 0.000 title claims abstract description 13
- 239000000758 substrate Substances 0.000 claims abstract description 64
- 238000001514 detection method Methods 0.000 claims abstract description 18
- 230000001678 irradiating effect Effects 0.000 claims abstract description 16
- 239000011148 porous material Substances 0.000 claims description 44
- 230000015572 biosynthetic process Effects 0.000 claims description 2
- 238000012545 processing Methods 0.000 description 24
- 230000003287 optical effect Effects 0.000 description 15
- 239000010949 copper Substances 0.000 description 11
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 description 9
- 238000000034 method Methods 0.000 description 9
- 238000002474 experimental method Methods 0.000 description 6
- 238000003384 imaging method Methods 0.000 description 5
- 230000001681 protective effect Effects 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000003754 machining Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 2
- 230000015654 memory Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
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- H—ELECTRICITY
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
- H01L21/76886—Modifying permanently or temporarily the pattern or the conductivity of conductive members, e.g. formation of alloys, reduction of contact resistances
- H01L21/76892—Modifying permanently or temporarily the pattern or the conductivity of conductive members, e.g. formation of alloys, reduction of contact resistances modifying the pattern
- H01L21/76894—Modifying permanently or temporarily the pattern or the conductivity of conductive members, e.g. formation of alloys, reduction of contact resistances modifying the pattern using a laser, e.g. laser cutting, laser direct writing, laser repair
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
- B23K26/40—Removing material taking account of the properties of the material involved
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76898—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics formed through a semiconductor substrate
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/03—Observing, e.g. monitoring, the workpiece
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
- B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
- B23K26/0624—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses using ultrashort pulses, i.e. pulses of 1ns or less
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/08—Devices involving relative movement between laser beam and workpiece
- B23K26/083—Devices involving movement of the workpiece in at least one axial direction
- B23K26/0853—Devices involving movement of the workpiece in at least in two axial directions, e.g. in a plane
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
- B23K26/362—Laser etching
- B23K26/364—Laser etching for making a groove or trench, e.g. for scribing a break initiation groove
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
- B23K26/38—Removing material by boring or cutting
- B23K26/382—Removing material by boring or cutting by boring
- B23K26/386—Removing material by boring or cutting by boring of blind holes
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/36—Removing material
- B23K26/40—Removing material taking account of the properties of the material involved
- B23K26/402—Removing material taking account of the properties of the material involved involving non-metallic material, e.g. isolators
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02107—Forming insulating materials on a substrate
- H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
- H01L21/02203—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates the layer being porous
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/34—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies not provided for in groups H01L21/0405, H01L21/0445, H01L21/06, H01L21/16 and H01L21/18 with or without impurities, e.g. doping materials
- H01L21/42—Bombardment with radiation
- H01L21/423—Bombardment with radiation with high-energy radiation
- H01L21/428—Bombardment with radiation with high-energy radiation using electromagnetic radiation, e.g. laser radiation
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- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/36—Electric or electronic devices
- B23K2101/42—Printed circuits
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2103/00—Materials to be soldered, welded or cut
- B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
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Abstract
Description
本発明は、基板の裏面にレーザー光線を照射して電極パッドに至る細孔を形成するレーザー加工方法に関する。 The present invention relates to a laser processing method in which a back surface of a substrate is irradiated with a laser beam to form pores reaching electrode pads.
ＩＣ、ＬＳＩ等のデバイスが分割予定ラインによって区画され表面に形成されたウエーハは、ダイシング装置、レーザー加工装置によって個々のデバイスチップに分割され、携帯電話、パソコン等の電気機器に利用される。 A wafer formed on the surface by dividing devices such as IC and LSI by dividing lines is divided into individual device chips by a dicing device and a laser processing device, and used for electric equipment such as mobile phones and personal computers.
近年では、該デバイスが形成された基板の裏面側から、該デバイスに形成された電極パッドの裏面に達する細孔（ビアホール）を形成し、その後、該細孔にアルミニウム等の導電性部材を埋設して上下にデバイスを積層することでデバイスの高機能化が図られている。 In recent years, a pore (via hole) reaching the back surface of an electrode pad formed on the device is formed from the back surface side of the substrate on which the device is formed, and then a conductive member such as aluminum is embedded in the pore. By stacking the devices on top of each other, the functionality of the device is enhanced.
本出願人は、上記した細孔を形成すべく、デバイスの電極パッドに対応する基板の裏面にレーザー光線を照射して細孔を形成する技術を提案している（特許文献１を参照。）。この特許文献１に記載された技術では、デバイスが表面に形成された基板の裏面にレーザー光線を照射することで発せられるプラズマ光と、レーザー光線が電極パッドに達することで発せられるプラズマ光とを検出し、電極パッドにレーザー光線が到達したことを該プラズマ光により判定することで、電極パッドに穴を開けることなくレーザー光線を停止させようとするものである。 The present applicant has proposed a technique of irradiating a laser beam on the back surface of the substrate corresponding to the electrode pad of the device to form the pores (see Patent Document 1). In the technique described in Patent Document 1, the device detects plasma light emitted by irradiating the back surface of the substrate formed on the surface with a laser beam and plasma light emitted by the laser beam reaching the electrode pad. By determining that the laser beam has reached the electrode pad by the plasma light, the laser beam is stopped without making a hole in the electrode pad.
上記した従来技術によれば、基板の裏面側から照射されたレーザー光線が電極パッドに達することで、電極パッドを構成する物質固有のプラズマ光が発生するため、該物質固有のプラズマ光を検出した際に、レーザー光線を停止する。しかし、レーザー光線のスポット径は電極パッドの面積に比べて小さく設定されるため、後に細孔に埋設される導電性部材と電極パッドとを確実に接続するためには、電極パッドを充分に露出させるべくレーザー光線が電極パッドに最初に達してからもある程度繰り返してレーザー光線を照射する必要がある。 According to the above-mentioned conventional technique, when the laser beam irradiated from the back surface side of the substrate reaches the electrode pad, plasma light peculiar to the substance forming the electrode pad is generated. Then, turn off the laser beam. However, since the spot diameter of the laser beam is set to be smaller than the area of the electrode pad, the electrode pad must be sufficiently exposed in order to reliably connect the conductive member and the electrode pad, which will be buried in the pores later. Therefore, it is necessary to repeat the laser beam to some extent after the laser beam first reaches the electrode pad.
他方、デバイス上に形成された電極パッドはその面積が狭く、該電極パッド全域を含むようにレーザー光線の照射領域を設定した場合、ある程度電極パッドが露出した後もレーザー光線が基板に当たり、該基板を構成する物質固有のプラズマ光が出続けるため、電極パッドを構成する物質固有のプラズマ光を充分に検出することができず、その結果、電極パッドにレーザー光線が過剰に照射されることで電極パッドに穴が開いてしまい、適正に細孔を形成することが困難であるという問題がある。 On the other hand, the electrode pad formed on the device has a small area, and when the irradiation area of the laser beam is set so as to include the entire area of the electrode pad, the laser beam hits the substrate even after the electrode pad is exposed to some extent, and the substrate is formed. As the plasma light peculiar to the substance continues to be emitted, it is not possible to sufficiently detect the plasma light peculiar to the substance forming the electrode pad, and as a result, the laser beam is excessively irradiated to the electrode pad, which causes holes in the electrode pad. However, there is a problem that it is difficult to properly form the pores.
本発明は、上記事実に鑑みなされたものであり、その主たる技術課題は、デバイスの電極パッドに対応する基板の裏面からレーザー光線を照射して適正に細孔を形成することができるレーザー加工方法を提供することにある。 The present invention has been made in view of the above facts, and its main technical problem is to provide a laser processing method capable of appropriately forming pores by irradiating a laser beam from the back surface of a substrate corresponding to an electrode pad of a device. To provide.
上記主たる技術課題を解決するため、本発明によれば、電極パッドを備えたデバイスが表面に形成された基板の裏面にレーザー光線を照射して電極パッドに至る細孔を形成するレーザー加工方法であって、電極パッドに対応する裏面からレーザー光線を照射するレーザー光線照射工程と、レーザー光線の照射によって基板に細孔が形成されると共に基板から発せられる第一のプラズマ光と電極パッドから発せられる第二のプラズマ光とを検出する検出工程と、該検出工程において、該第二のプラズマ光を検出した際、レーザー光線の照射を停止するレーザー照射終了工程と、を少なくとも含み、該レーザー光線照射工程の前に、該電極パッドの大きさを検出し、形成される細孔が該電極パッドの内側に位置するようにレーザー光線の照射領域を設定する照射領域設定工程が実施されるレーザー加工方法が提供される。 In order to solve the above-mentioned main technical problem, according to the present invention, a device provided with an electrode pad is a laser processing method of irradiating a laser beam to the back surface of a substrate formed on the surface to form pores reaching the electrode pad. Laser beam irradiation step of irradiating a laser beam from the back surface corresponding to the electrode pad, and the first plasma light emitted from the substrate and the second plasma emitted from the electrode pad as well as the formation of pores in the substrate by the laser beam irradiation. A detection step of detecting light and a laser irradiation termination step of stopping irradiation of a laser beam when the second plasma light is detected in the detection step, and at least including the laser beam irradiation step before the laser beam irradiation step. Laser beam irradiation area so that the size of the electrode pad is detected and the pores formed are located inside the electrode pad Laser processing method irradiation region setting step of setting is performed is provided.
該照射領域設定工程において、該電極パッドに内接する円の面積に対して電極パッドに形成される細孔の断面積が９５％以下になるようにレーザー光線の該照射領域を設定することが好ましい。 In the irradiation region setting step, it is preferable to set the irradiation region of the laser beam so that the cross-sectional area of the pores formed in the electrode pad is 95% or less with respect to the area of the circle inscribed in the electrode pad.
本発明のレーザー加工方法は、電極パッドを備えたデバイスが表面に形成された基板の裏面にレーザー光線を照射して電極パッドに至る細孔を形成するレーザー加工方法であって、電極パッドに対応する裏面からレーザー光線を照射するレーザー光線照射工程と、レーザー光線の照射によって基板に細孔が形成されると共に基板から発せられる第一のプラズマ光と電極パッドから発せられる第二のプラズマ光とを検出する検出工程と、該検出工程において、該第二のプラズマ光を検出した際、レーザー光線の照射を停止するレーザー照射終了工程と、を少なくとも含み、該レーザー光線照射工程の前に、該電極パッドの大きさを検出し、形成される細孔が該電極パッドの内側に位置するようにレーザー光線の照射領域を設定する照射領域設定工程が実施される。これにより、電極パッドに細孔が至った際に、レーザー光線が確実に電極パッドに照射され、第二のプラズマ光を充分に検出することができ、電極パッドに穴が開くという問題が解消する。 The laser processing method of the present invention is a laser processing method in which a device provided with an electrode pad is irradiated with a laser beam on the back surface of a substrate formed on the surface to form pores reaching the electrode pad, and corresponds to the electrode pad. A laser beam irradiation step of irradiating a laser beam from the back surface, and a detection step of detecting a first plasma light emitted from the substrate and a second plasma light emitted from the electrode pad as well as pores are formed in the substrate by the irradiation of the laser beam. And a laser irradiation ending step of stopping the irradiation of the laser beam when the second plasma light is detected in the detecting step, and the size of the electrode pad is detected before the laser beam applying step. And setting the irradiation area of the laser beam so that the formed pores are located inside the electrode pad. Degree is carried out. With this, when the pore reaches the electrode pad, the laser beam is surely applied to the electrode pad, the second plasma light can be sufficiently detected, and the problem that the electrode pad has a hole is solved.
以下、本発明に基づき構成されるレーザー加工方法に係る実施形態について添付図面を参照して、更に詳細に説明する。 Hereinafter, embodiments of a laser processing method configured according to the present invention will be described in more detail with reference to the accompanying drawings.
図１には、本実施形態においてレーザー加工される被加工物として用意される円盤状の基板１０の斜視図が示されている。図１に示す基板１０は、例えば、厚みが３００μｍのリチウムタンタレート（ＬＴ）で構成され、表面１０ａに格子状に配列された複数の分割予定ライン１４によって複数の領域が区画され、この区画された領域にデバイス１２がそれぞれ形成されている。デバイス１２の表面には、図１におけるＡ部を右方に拡大して示すように、略矩形状の複数（１０個）の電極パッド１２ａが形成されている。この電極パッド１２ａは、５００μｍ×６００μｍ程度の大きさであり、図示の実施形態においては銅（Ｃｕ）によって形成されている。用意された基板１０は、図１に示すように、環状のフレームＦに装着された保護テープＴに対して表面１０ａ側を下に、裏面１０ｂを上側にして貼着され支持される。 FIG. 1 shows a perspective view of a disk-shaped substrate 10 prepared as a workpiece to be laser processed in this embodiment. The substrate 10 shown in FIG. 1 is made of, for example, lithium tantalate (LT) having a thickness of 300 μm, and a plurality of dividing lines 14 arranged in a grid pattern on the surface 10 a divide a plurality of regions. The devices 12 are formed in the respective regions. A plurality of (10) electrode pads 12a having a substantially rectangular shape are formed on the surface of the device 12, as shown by enlarging the portion A in FIG. 1 to the right. The electrode pad 12a has a size of about 500 μm × 600 μm, and is made of copper (Cu) in the illustrated embodiment. As shown in FIG. 1, the prepared substrate 10 is attached and supported with the front surface 10a side facing downward and the back surface 10b facing upward with respect to the protective tape T mounted on the annular frame F.
図２には、本実施形態において基板１０に対してレーザー光線を照射するレーザー加工装置１の全体斜視図が示されている。レーザー加工装置１は、フレームＦに保護テープＴを介して支持された基板１０を保持する保持手段２０と、保持手段２０を移動させる移動手段３０と、保持手段２０に保持された基板１０にレーザー加工を施すレーザー光線照射手段５０と、保持手段２０に保持される基板１０を撮像する撮像手段６０と、基板１０から発せられるプラズマ光を検出するプラズマ検出手段７０と、を備えている。 FIG. 2 shows an overall perspective view of the laser processing apparatus 1 that irradiates the substrate 10 with a laser beam in the present embodiment. The laser processing apparatus 1 includes a holding unit 20 that holds the substrate 10 supported by the frame F via the protective tape T, a moving unit 30 that moves the holding unit 20, and a laser on the substrate 10 held by the holding unit 20. A laser beam irradiation means 50 for processing, an image pickup means 60 for picking up an image of the substrate 10 held by the holding means 20, and a plasma detection means 70 for detecting plasma light emitted from the substrate 10 are provided.
保持手段２０は、図中に矢印Ｘで示すＸ軸方向において移動自在に基台２に載置される矩形状のＸ軸方向可動板２１と、該Ｘ軸方向と直交し、該Ｘ軸方向と実質水平面を構成する矢印Ｙで示すＹ軸方向において移動自在にＸ軸方向可動板２１上に載置される矩形状のＹ軸方向可動板２２と、Ｙ軸方向可動板２２の上面に固定された円筒状の支柱２４と、支柱２４の上端に固定された矩形状のカバー板２６とを含む。カバー板２６には、カバー板２６上に形成された長穴を通って上方に延びる円形状のチャックテーブル２８が配設されている。チャックテーブル２８は基板１０を保持し、支柱２４内に収容された図示しない回転駆動手段により回転可能に構成されている。チャックテーブル２８の上面には、多孔質材料から形成され実質上水平に延在する円形状の吸着チャック４０が配置されている。吸着チャック４０は、支柱２４の内部を通る流路によって図示しない吸引手段に接続されている。チャックテーブル２８には、基板１０を支持するフレームＦを固定するためのクランプ４２が配設されている。 The holding means 20 is a rectangular X-axis direction movable plate 21 that is mounted on the base 2 so as to be movable in the X-axis direction indicated by an arrow X in the figure, and is orthogonal to the X-axis direction, and the X-axis direction. And a rectangular Y-axis direction movable plate 22 movably mounted on the X-axis direction movable plate 21 in the Y-axis direction shown by the arrow Y forming a substantially horizontal plane, and fixed to the upper surface of the Y-axis direction movable plate 22. It includes a cylindrical support 24 and a rectangular cover plate 26 fixed to the upper end of the support 24. The cover plate 26 is provided with a circular chuck table 28 extending upward through a long hole formed on the cover plate 26. The chuck table 28 holds the substrate 10 and is configured to be rotatable by a rotation driving unit (not shown) housed in the column 24. On the upper surface of the chuck table 28, a circular suction chuck 40 formed of a porous material and extending substantially horizontally is arranged. The suction chuck 40 is connected to a suction unit (not shown) by a flow path passing through the inside of the support column 24. A clamp 42 for fixing the frame F supporting the substrate 10 is arranged on the chuck table 28.
移動手段３０は、基台２上に配設され、保持手段２０とレーザー光線照射手段５０とを相対的に移動させる手段として備えられるものであり、保持手段２０をＸ軸方向に加工送りするＸ軸移動手段３１と、保持手段２０をＹ軸方向に割り出し送りするＹ軸移動手段３２と、を備えている。Ｘ軸移動手段３１は、パルスモータ３１ａの回転運動をボールねじ３１ｂを介して直線運動に変換してＸ軸方向可動板２１に伝達し、基台２上の案内レール２ａ、２ａに沿ってＸ軸方向可動板２１をＸ軸方向において進退させる。Ｙ軸移動手段３２は、パルスモータ３２ａの回転運動を、ボールねじ３２ｂを介して直線運動に変換してＹ軸方向可動板２２に伝達し、Ｘ軸方向可動板２１上の案内レール２１ａ、２１ａに沿ってＹ軸方向可動板２２をＹ軸方向において進退させる。さらに、支柱２４の内部には図示しない回転駆動手段が収容されており、チャックテーブル２８の位置を任意の角度に回転させて制御することが可能に構成されている。なお、図示は省略するが、Ｘ軸移動手段３１、Ｙ軸移動手段３２、及び回転駆動手段には、位置検出手段が配設されており、基台２上におけるチャックテーブル２８のＸ軸方向の位置、Ｙ軸方向の位置、周方向の回転位置が正確に検出され、後述する制御手段１００（図３を参照。）に伝達されることで、制御手段１００から指示される指示信号に基づいてＸ軸移動手段３１、Ｙ軸移動手段３２、及び図示しない回転駆動手段が駆動され、所望のＸ座標位置、Ｙ座標位置、及び角度θになるようにチャックテーブル２８の位置を制御することが可能である。 The moving means 30 is provided on the base 2 and is provided as means for relatively moving the holding means 20 and the laser beam irradiation means 50, and an X axis for processing and feeding the holding means 20 in the X axis direction. The moving means 31 and the Y-axis moving means 32 for indexing and feeding the holding means 20 in the Y-axis direction are provided. The X-axis moving means 31 converts the rotational motion of the pulse motor 31a into a linear motion via the ball screw 31b and transmits the linear motion to the X-axis direction movable plate 21, and the X-axis moving along the guide rails 2a, 2a on the base 2. The axially movable plate 21 is moved back and forth in the X-axis direction. The Y-axis moving means 32 converts the rotational movement of the pulse motor 32a into a linear movement via the ball screw 32b and transmits it to the Y-axis direction movable plate 22, and guide rails 21a, 21a on the X-axis direction movable plate 21. The Y-axis direction movable plate 22 is moved back and forth along the Y-axis direction. Further, a rotation driving means (not shown) is housed inside the column 24, and the position of the chuck table 28 can be rotated at an arbitrary angle to be controlled. Although not shown, the X-axis moving means 31, the Y-axis moving means 32, and the rotation driving means are provided with position detecting means, and the chuck table 28 on the base 2 in the X-axis direction. The position, the position in the Y-axis direction, and the rotational position in the circumferential direction are accurately detected and transmitted to the control unit 100 (see FIG. 3) described later, and based on the instruction signal instructed from the control unit 100. The X-axis moving means 31, the Y-axis moving means 32, and a rotation driving means (not shown) are driven, and the position of the chuck table 28 can be controlled so that the desired X coordinate position, Y coordinate position, and angle θ can be obtained. Is.
移動手段３０の側方には、枠体４が立設される。枠体４は、基台２上に配設される垂直壁部４ａ、及び垂直壁部４ａの上端部から水平方向に延びる水平壁部４ｂと、を備えている。枠体４の水平壁部４ｂの内部には、図示しないレーザー光線照射手段５０の光学系が内蔵されている。水平壁部４ｂの先端部下面には、レーザー光線照射手段５０の一部を構成する集光器５２が配設されている。レーザー光線照射手段５０において発振されたレーザー光線は、保持手段２０に保持される基板１０の所望の位置に照射される。 The frame 4 is erected on the side of the moving means 30. The frame body 4 includes a vertical wall portion 4a arranged on the base 2, and a horizontal wall portion 4b extending horizontally from an upper end portion of the vertical wall portion 4a. Inside the horizontal wall portion 4b of the frame body 4, an optical system of a laser beam irradiation means 50 (not shown) is built in. A condenser 52 that constitutes a part of the laser beam irradiation means 50 is disposed on the lower surface of the tip of the horizontal wall 4b. The laser beam oscillated by the laser beam application means 50 is applied to a desired position on the substrate 10 held by the holding means 20.
レーザー光線照射手段５０は、図３に示すように、パルス状のレーザー光線ＬＢを発振するパルスレーザー光線発振器５１と、パルスレーザー光線発振器５１が発振したレーザー光線ＬＢの出力を調整するアッテネータ５３と、レーザー光線ＬＢの光路を任意の加工送り方向（Ｘ軸方向）に偏向制御する光偏向手段として少なくとも音響光学素子を含む第一の音響光学偏向手段５４と、レーザー光線ＬＢの光路を任意の割り出し送り方向（Ｙ軸方向）に偏向制御する光偏向手段として少なくとも音響光学素子を含む第二の音響光学偏向手段５５と、第二の音響光学偏向手段５５からのレーザー光線ＬＢの光路の方向を変換する反射ミラー５６と、を備え、反射ミラー５６から反射されたパルスレーザー光線ＬＢの光路を、ｆθレンズを備えた集光器５２に導くように構成されている。上記したパルスレーザー光線発振器５１、アッテネータ５３、第一の音響光学偏向手段５４、第二の音響光学偏向手段５５は、制御手段１００に接続され、制御手段１００から送信される指示信号に基づいてその作動が制御される。 As shown in FIG. 3, the laser beam irradiation means 50 includes a pulse laser beam oscillator 51 that oscillates a pulsed laser beam LB, an attenuator 53 that adjusts the output of the laser beam LB oscillated by the pulse laser beam oscillator 51, and an optical path of the laser beam LB. A first acousto-optic deflecting means 54 including at least an acousto-optic element as a light deflecting means for controlling deflection in an arbitrary processing feed direction (X axis direction), and an optical path of the laser beam LB in an arbitrary indexing feed direction (Y axis direction). A second acousto-optical deflecting means 55 including at least an acousto-optical element as a light deflecting means for controlling deflection, and a reflecting mirror 56 for converting the direction of the optical path of the laser beam LB from the second acousto-optical deflecting means 55 are provided. An optical path of the pulse laser beam LB reflected from the reflection mirror 56 is provided with an fθ lens. It is configured to direct the optical device 52. The pulse laser beam oscillator 51, the attenuator 53, the first acousto-optic deflecting means 54, and the second acousto-optic deflecting means 55 described above are connected to the control means 100 and operate based on an instruction signal transmitted from the control means 100. Is controlled.
第一の音響光学偏向手段５４に対し、制御手段１００から例えば５Ｖの電圧が印加され、図示しない音響光学素子に５Ｖに対応する周波数が印加された場合には、パルスレーザー光線発振器５１から発振されたレーザー光線ＬＢは、その光軸が図３においてＬＢ１で示すように偏向され集光点Ｐ１に集光される。また、第一の音響光学偏向手段５４に制御手段１００から例えば１０Ｖの電圧が印加され、該音響光学素子に１０Ｖに対応する周波数が印加された場合には、パルスレーザー光線発振器５１から発振されたレーザー光線ＬＢは、その光軸が図３においてＬＢ０で示すように偏向され、上記集光点Ｐ１から加工送り方向（Ｘ軸方向）に図３において右方に所定量変位した集光点Ｐ０に集光される。さらに、第一の音響光学偏向手段５４に制御手段１００から例えば１５Ｖの電圧が印加され、該音響光学素子に１５Ｖに対応する周波数が印加された場合には、パルスレーザー光線発振器５１から発振されたレーザー光線ＬＢは、その光軸が図３においてＬＢ２で示すように偏向され、上記集光点Ｐ０から加工送り方向（Ｘ軸方向）に図３においてさらに右方に所定量変位した集光点Ｐ２に集光される。第二の音響光学偏向手段５５は、上記した第一の音響光学偏向手段５４に対し、偏向方向が基板１０上の割り出し送り方向（Ｙ軸方向：図面に対して垂直な方向）である点でのみ相違し、それ以外は同様の動作をするように構成されている。このように、第一の音響光学偏向手段５４、及び第二の音響光学偏向手段５５によって偏向されるレーザー光線ＬＢは、印加される電圧に対応して加工送り方向（Ｘ軸方向）、割り出し送り方向（Ｙ軸方向）の所定の範囲において任意の位置に偏向させることができる。 When a voltage of, for example, 5V is applied from the control means 100 to the first acousto-optic deflecting means 54 and a frequency corresponding to 5V is applied to an acousto-optic element (not shown), the pulse laser beam oscillator 51 oscillates. The laser beam LB has its optical axis deflected as indicated by LB1 in FIG. 3 and is condensed at the condensing point P1. Further, when a voltage of, for example, 10 V is applied to the first acousto-optic deflecting means 54 from the control means 100 and a frequency corresponding to 10 V is applied to the acousto-optic element, the laser beam oscillated from the pulse laser beam oscillator 51. The optical axis of LB is deflected as indicated by LB0 in FIG. 3, and the light is condensed at the light condensing point P0 displaced from the light condensing point P1 in the machining feed direction (X-axis direction) to the right in FIG. 3 by a predetermined amount. To be done. Further, when a voltage of, for example, 15 V is applied to the first acousto-optic deflecting means 54 from the control means 100 and a frequency corresponding to 15 V is applied to the acousto-optic element, the laser beam oscillated from the pulse laser beam oscillator 51. The optical axis of the LB is deflected as shown by LB2 in FIG. 3, and the LB is converged on the condensing point P2 which is further displaced from the condensing point P0 to the right in FIG. Be illuminated. The second acousto-optic deflecting means 55 is different from the above-mentioned first acousto-optic deflecting means 54 in that the deflection direction is the indexing feed direction on the substrate 10 (Y-axis direction: direction perpendicular to the drawing). Only the difference is made, and other than that, the same operation is performed. As described above, the laser beam LB deflected by the first acousto-optic deflecting means 54 and the second acousto-optic deflecting means 55 corresponds to the applied voltage in the machining feed direction (X-axis direction) and the index feed direction. It can be deflected to an arbitrary position within a predetermined range in the (Y-axis direction).
制御手段１００は、コンピュータにより構成され、制御プログラムに従って演算を実行する中央演算処理装置（ＣＰＵ）と、制御プログラム等を格納するリードオンリメモリ（ＲＯＭ）と、検出した検出値、演算結果等を格納するための読み書き可能なランダムアクセスメモリ（ＲＡＭ）と、入力インターフェース、及び出力インターフェースとを備えている。制御手段１００には、上記したレーザー光線照射手段５０のみならず、移動手段３０、撮像手段６０、及びプラズマ光検出手段７０等が接続され、制御手段１００からの指示信号により制御可能に構成されている。 The control means 100 is composed of a computer, and a central processing unit (CPU) that executes an operation according to a control program, a read-only memory (ROM) that stores a control program and the like, and stores a detected value, an operation result, and the like. And a readable / writable random access memory (RAM) for input / output, an input interface, and an output interface. The control means 100 is connected not only to the laser beam irradiation means 50 described above but also to the moving means 30, the imaging means 60, the plasma light detecting means 70, etc., and is configured to be controllable by an instruction signal from the control means 100. .
撮像手段６０は、水平壁部４ｂの先端部下面において、集光器５２のＸ軸方向で隣接した位置に配設される。撮像手段６０は、可視光線により撮像する通常の撮像素子、被加工物を照明する照明手段、赤外線撮像素子、及び赤外線照射手段等を備え、撮像手段６０により撮像された画像情報は、制御手段１００に送信される。撮像手段６０は、レーザー加工を実施する際に、基板１０と集光器５２との位置合わせ（アライメント）を実施する際に使用されると共に、デバイス１２に形成された各電極パッド１２ａの大きさ等を検出するために使用される。 The image pickup means 60 is arranged at a position adjacent to the light collector 52 in the X-axis direction on the lower surface of the front end portion of the horizontal wall portion 4b. The image pickup means 60 includes a normal image pickup element for picking up an image with visible light, an illuminating means for illuminating a workpiece, an infrared ray image pickup element, an infrared ray irradiating means, and the like. Sent to. The imaging unit 60 is used when performing alignment between the substrate 10 and the condenser 52 when performing laser processing, and the size of each electrode pad 12a formed in the device 12 is also used. And so on.
プラズマ光検出手段７０の本体部は、枠体４の水平壁部４ｂに収容されており、プラズマ光検出手段７０の一部を構成するプラズマ受光手段７１は、図２に示すように、枠体４の水平壁部４ｂの先端部下面において、集光器５２のＸ軸方向で隣接した位置であって、撮像手段６０とは反対側の位置に取り付けられる。このプラズマ光検出手段７０は、図３に示すようにレーザー光線照射手段５０の集光器５２から照射されるレーザー光線ＬＢがチャックテーブル４０に保持された基板１０に照射されることによって発生するプラズマ光を受光するプラズマ受光手段７１と、プラズマ受光手段７１によって受光されたプラズマ光を第一の光路７２ａと第二の光路７２ｂに分岐するビームスプリッター７２と、第一の光路７２ａに配設され波長が第一の設定波長(基板１０の基板を形成するリチウムタンタレートが発する波長)の光のみを通過させる第一のバンドパスフィルター７３と、第一のバンドパスフィルター７３を通過した光を受光して光強度信号を出力する第一のホトデテクター７４と、第二の光路７２ｂに配設された方向変換ミラー７５と、方向変換ミラー７５によって方向変換された波長が第二の設定波長(電極パッド１２を形成する銅が発する波長)の光のみを通過させる第二のバンドパスフィルター７６と、第二のバンドパスフィルター７６を通過した光を受光して光強度信号を出力する第二のホトデテクター７７とを備えている。上記したプラズマ受光手段７１は、図示しない集光レンズと、該集光レンズを収容するレンズケースとからなっている。 The main body of the plasma light detecting means 70 is housed in the horizontal wall portion 4b of the frame body 4, and the plasma light receiving means 71 which constitutes a part of the plasma light detecting means 70, as shown in FIG. On the lower surface of the front end portion of the horizontal wall portion 4b of No. 4, the condenser 52 is attached at a position adjacent to the condenser 52 in the X-axis direction and on a side opposite to the image pickup means 60. The plasma light detecting means 70 generates plasma light generated by irradiating the substrate 10 held on the chuck table 40 with the laser beam LB emitted from the condenser 52 of the laser beam irradiating means 50 as shown in FIG. A plasma light receiving means 71 for receiving light, a beam splitter 72 for branching the plasma light received by the plasma light receiving means 71 into a first optical path 72a and a second optical path 72b, and a wavelength arranged in the first optical path 72a and having a wavelength of A first bandpass filter 73 that allows only light of one set wavelength (wavelength emitted by lithium tantalate forming the substrate of the substrate 10) and light that has passed through the first bandpass filter 73 to be received A first photodetector 74 for outputting an intensity signal, a direction changing mirror 75 arranged in the second optical path 72b, and a direction changing The second bandpass filter 76 that allows only the light of the second set wavelength (the wavelength emitted by the copper forming the electrode pad 12) whose wavelength is changed by the laser 75 and the second bandpass filter 76 to pass therethrough. The second photo detector 77 that receives the generated light and outputs a light intensity signal is provided. The plasma light receiving means 71 is composed of a condenser lens (not shown) and a lens case that accommodates the condenser lens.
上記した第一のバンドパスフィルター７３は、図示の実施形態においてはリチウムタンタレートから発せられる第一のプラズマ光の波長（６７０ｎｍ）のみを通過させるために波長が６６０〜６８０ｎｍの範囲の光を通過させるようになっている。また、上記した第二のバンドパスフィルター７６は図示の実施形態においては銅から発せられる第二のプラズマ光の波長（５１５ｎｍ）のみを通過させるために波長が５１０〜５２０ｎｍの範囲の光を通過させるようになっている。図示の実施形態におけるプラズマ検出手段７０は以上のように構成されており、第一のホトデテクター７４、及び第二のホトデテクター７７は、受光した光強度に対応する電圧値の信号を制御手段１００に出力する。 In the illustrated embodiment, the above-mentioned first band-pass filter 73 passes light in the wavelength range of 660 to 680 nm in order to pass only the wavelength (670 nm) of the first plasma light emitted from lithium tantalate. It is designed to let you. Further, in the illustrated embodiment, the above-mentioned second bandpass filter 76 allows only the wavelength (515 nm) of the second plasma light emitted from copper to pass therethrough, and thus allows the light in the wavelength range of 510 to 520 nm to pass. It is like this. The plasma detection means 70 in the illustrated embodiment is configured as described above, and the first photodetector 74 and the second photodetector 77 output a voltage value signal corresponding to the received light intensity to the control means 100. To do.
本実施形態で使用されるレーザー加工装置１は概ね上記したように構成されており、上記したレーザー加工装置１を用い、基板１０に形成された各デバイス１２の電極パッド１２ａに対応する位置に、基板１０の裏面１０ｂ側から電極パッド１２ａに達する細孔（ビアホール）を形成するレーザー加工の実施形態について説明する。 The laser processing apparatus 1 used in the present embodiment is generally configured as described above. Using the laser processing apparatus 1 described above, the laser processing apparatus 1 is formed at a position corresponding to the electrode pad 12a of each device 12 formed on the substrate 10. An embodiment of laser processing for forming pores (via holes) reaching the electrode pads 12a from the back surface 10b side of the substrate 10 will be described.
基板１０は、上記したように、裏面１０ｂ側を上側にして環状のフレームＦに保護テープＴを介して支持されており、図２に示すレーザー加工装置１のチャックテーブル２８の吸着チャック４０上に保護テープＴ側を下にして載置する。そして、基板１０は、図示しない吸引手段を作動することにより、保護テープＴを介してチャックテーブル２８に吸引保持され、環状のフレームＦは、クランプ４２によって固定される。 As described above, the substrate 10 is supported by the annular frame F via the protective tape T with the back surface 10b side facing upward, and is placed on the suction chuck 40 of the chuck table 28 of the laser processing apparatus 1 shown in FIG. Place the protective tape T side down. Then, the substrate 10 is suction-held on the chuck table 28 via the protective tape T by operating suction means (not shown), and the annular frame F is fixed by the clamp 42.
上述したように基板１０を吸引保持したチャックテーブル２８は、Ｘ軸移動手段３１によって撮像手段６０の直下に位置付けられる。チャックテーブル２８が撮像手段６０の直下に位置付けられると、チャックテーブル２８に保持された基板１０に形成されている格子状の分割予定ライン１４がＸ軸方向とＹ軸方向に平行に位置付けられているか否かを確認して基板１０の方向を調整するアライメント作業を実施する。 The chuck table 28 holding the substrate 10 by suction as described above is positioned directly below the image pickup means 60 by the X-axis moving means 31. When the chuck table 28 is positioned directly below the image pickup means 60, is the grid-like planned dividing line 14 formed on the substrate 10 held by the chuck table 28 positioned parallel to the X-axis direction and the Y-axis direction? It is confirmed whether or not the alignment work for adjusting the direction of the substrate 10 is performed.
上記したように、チャックテーブル２８に保持された基板１０のアライメントを実施したならば、次いで、各デバイス１２に形成されている電極パッド１２ａの大きさを検出し、追って実施されるレーザー光線照射工程において形成される細孔が電極パッド１２ａの内側に位置するようにレーザー光線ＬＢの照射領域を設定する照射領域設定工程を実施する。図４、図５を参照しながらより具体的に説明する。 After the substrate 10 held on the chuck table 28 is aligned as described above, the size of the electrode pad 12a formed on each device 12 is detected, and the size of the electrode pad 12a formed in each device 12 is detected in the laser beam irradiation step which is performed later. The irradiation region setting step of setting the irradiation region of the laser beam LB is performed so that the formed pores are located inside the electrode pad 12a. A more specific description will be given with reference to FIGS. 4 and 5.
（照射領域設定工程）
まず、デバイス１２に形成された電極パッド１２ａを撮像手段６０で撮像される領域の中央に位置付ける。撮像手段６０には、上記したように赤外線照射手段、赤外線撮像素子が備えられており、図４（ａ）に示されているように、基板１０の表面１０ａ側に形成されたデバイス１２の電極パッド１２ａ（点線で示す。）を撮像することができる。撮像手段６０によって撮像された電極パッド１２ａの画像情報は制御手段１００に送られて、電極パッド１２ａの大きさ、形状等を確認する。その後、図に示された略矩形状の電極パッド１２ａの形状を考慮して、電極パッド１２ａに内接する円（内接円）１２１を特定する（２点鎖線で示す。）。内接円１２１を特定したならば、内接円１２１の直径を特定し内接円１２１の面積を演算する。本実施形態では、電極パッド１２ａの内接円１２１の直径は５００μｍであることから、面積は、６２，５００πμｍ２（０．０６２５πｍｍ２）である。この内接円１２１の面積が演算されたならば、レーザー光線ＬＢが照射される照射領域を設定する際の面積の最大値となる基準値を演算する。本実施形態では、該基準値は、内接円１２１の面積の９５％であり、以下の如く演算する。
６２，５００πμｍ２×０．９５
＝５９，３７５πμｍ２（＝０．０５９３７５πｍｍ２）
(Irradiation area setting process)
First, the electrode pad 12a formed on the device 12 is positioned at the center of the area imaged by the imaging means 60. The image pickup means 60 is provided with the infrared ray irradiation means and the infrared ray image pickup element as described above, and as shown in FIG. 4A, the electrodes of the device 12 formed on the surface 10 a side of the substrate 10. The pad 12a (shown by a dotted line) can be imaged. The image information of the electrode pad 12a picked up by the image pickup means 60 is sent to the control means 100 to confirm the size, shape, etc. of the electrode pad 12a. After that, a circle (inscribed circle) 121 inscribed in the electrode pad 12a is specified in consideration of the shape of the substantially rectangular electrode pad 12a shown in the drawing (indicated by a chain double-dashed line). After the inscribed circle 121 is specified, the diameter of the inscribed circle 121 is specified and the area of the inscribed circle 121 is calculated. In this embodiment, since the diameter of the inscribed circle 121 of the electrode pad 12a is 500 μm, the area is 62,500πμm 2 (0.0625πmm 2 ). When the area of the inscribed circle 121 is calculated, the reference value that is the maximum value of the area when setting the irradiation region to be irradiated with the laser beam LB is calculated. In the present embodiment, the reference value is 95% of the area of the inscribed circle 121 and is calculated as follows.
62,500 πμm 2 × 0.95
= 59,375πμm 2 (= 0.059375πmm 2 )
上記した基準値に基づいて、面積が上記した基準値となる円（基準円）の半径を演算すると、略２４３．６７μｍとなる。すなわち、本実施形態では、レーザー光線ＬＢの照射領域１２２ａを、直径が４８７．３４μｍの該基準円と同等以下となるように設定する。 When the radius of the circle (reference circle) whose area is the above-mentioned reference value is calculated based on the above-mentioned reference value, it is approximately 243.67 μm. That is, in this embodiment, the irradiation area 122a of the laser beam LB is set to be equal to or less than the reference circle having a diameter of 487.34 μm.
本実施形態においては、レーザー光線ＬＢが照射される照射領域について、図４（ｂ）に示すように、上記した電極パッド１２ａの形状、大きさから演算される基準円と同等以下となるように、直径が４５０μｍの円１２２を外形とするレーザー光線ＬＢの照射領域１２２ａを設定する。この照射領域１２２ａは、上記した内接円１２１と中心が一致するようにその位置も設定され、内接円１２１が内接する電極パッド１２ａの各辺から均等に内側に離間するように設定される。このようにして、電極パッド１２ａにおける照射領域１２２ａが設定されたならば、照射領域１２２ａの大きさ（直径）、中心の座標位置等の情報が電極パッド１２ａに対応した情報として制御手段１００に記憶される。このような照射領域設定工程を基板１０上に形成された各デバイス１２、各電極パッド１２ａについて実施し、各デバイス１２の各電極パッド１２ａに対応して設定される照射領域１２２ａの情報が制御手段１００のランダムアクセスメモリ（ＲＡＭ）に記憶される。以上により、照射領域設定工程が完了する。照射領域設定工程が完了したならば、電極パッド１２ａに対応する裏面１０ｂからレーザー光線ＬＢを照射するレーザー光線照射工程を実施する。 In the present embodiment, the irradiation area irradiated with the laser beam LB is, as shown in FIG. 4B, equal to or less than the reference circle calculated from the shape and size of the electrode pad 12a described above. An irradiation region 122a of the laser beam LB having a contour of a circle 122 having a diameter of 450 μm is set. The position of the irradiation area 122a is set so that the center coincides with the inscribed circle 121 described above, and the irradiation area 122a is set so as to be evenly spaced inward from each side of the electrode pad 12a inscribed therein. . When the irradiation area 122a in the electrode pad 12a is set in this way, information such as the size (diameter) of the irradiation area 122a and the coordinate position of the center is stored in the control means 100 as information corresponding to the electrode pad 12a. To be done. Such an irradiation region setting step is performed for each device 12 and each electrode pad 12a formed on the substrate 10, and information of the irradiation region 122a set corresponding to each electrode pad 12a of each device 12 is the control means. It is stored in 100 random access memories (RAMs). With the above, the irradiation region setting step is completed. When the irradiation region setting step is completed, the laser beam irradiation step of irradiating the laser beam LB from the back surface 10b corresponding to the electrode pad 12a is performed.
なお、本発明の照射領域設定工程では、全ての電極パッド１２ａ毎に電極パッド１２ａの大きさを検出して照射領域１２２ａを一つ一つ設定する必要はなく、代表する１つの電極パッド１２ａの大きさを検出して照射領域１２２ａの大きさを設定し、その照射領域１２２ａの大きさを他の電極パッド１２ａの照射領域１２２ａとして適用するようにしてもよい。また、照射領域設定工程は、上記したアライメントを終了した後に実施することに限定されず、アライメントの前に実施することも可能であり、さらに、図２に記載されたレーザー加工装置１に基板１０を搬送する前に、事前に基板１０の表面１０ａ側から電極パッド１２ａを撮像して各電極パッド１２ａに対応する照射領域１２２ａの設定を行うこともできる。さらにいえば、基板１０上にデバイス１２を形成する際の製造公差が小さい場合は、実際に電極パッドを撮像して照射領域１２２ａを設定することに限定されず、設計図面上で電極パッドの大きさを検出（演算）し、照射領域１２２ａを設定するものであってもよい。 In the irradiation area setting step of the present invention, it is not necessary to detect the size of the electrode pad 12a for every electrode pad 12a and set each irradiation area 122a one by one. The size of the irradiation region 122a may be set by detecting the size, and the size of the irradiation region 122a may be applied as the irradiation region 122a of another electrode pad 12a. The irradiation region setting step is not limited to being performed after the above-described alignment is completed, and may be performed before the alignment. Furthermore, the laser processing apparatus 1 shown in FIG. It is also possible to image the electrode pads 12a from the front surface 10a side of the substrate 10 and set the irradiation region 122a corresponding to each electrode pad 12a in advance before the transfer. Furthermore, when the manufacturing tolerance when forming the device 12 on the substrate 10 is small, the size of the electrode pad is not limited to the actual size of the electrode pad set by imaging the electrode pad and setting the irradiation region 122a. The irradiation area 122a may be set by detecting (calculating) the height.
（レーザー光線照射工程）
上記したように、アライメント、照射領域設定工程を終えた状態で、レーザー光線照射工程を実施する。チャックテーブル２８に保持された基板１０の各デバイス１２、電極パッド１２ａの座標位置は、制御手段１００に記憶され管理されており、上記したアライメント、及び照射領域設定工程が実施されることで、基板１０上の電極パッド１２ａを任意の位置に正確に位置付けることが可能になっている。
(Laser beam irradiation process)
As described above, the laser beam irradiation step is performed in the state where the alignment and irradiation area setting steps have been completed. The coordinate position of each device 12 and the electrode pad 12a of the substrate 10 held on the chuck table 28 is stored and managed by the control means 100, and the alignment and the irradiation region setting process described above are performed, so that the substrate It is possible to accurately position the electrode pad 12a on 10 at an arbitrary position.
ここで、基板１０の裏面１０ｂ側から所望のデバイス１２の電極パッド１２ａに達する細孔を形成すべく、レーザー加工を開始するデバイス１２、及び電極パッド１２ａを定める。次いで、移動手段３０を作動してチャックテーブル２８を移動して、上記制御手段１００に格納されている電極パッド１２ａの座標位置情報に基づき、細孔を形成する電極パッド１２ａに対応する位置を、レーザー光線照射手段５０の集光器５２の直下に位置付ける。このように集光器５２の直下に電極パッド１２ａを位置付けた状態から、Ｘ軸移動手段３１を作動して所定の速度でＸ軸方向に加工送りを開始し、集光器５２から照射されるレーザー光線ＬＢの照射可能な範囲に電極パッド１２ａに対応して設定された照射領域１２２ａがあるか否かを判断し、レーザー光線ＬＢが照射される範囲に照射領域１２２ａが入っていると判断された状態で、レーザー光線照射手段５０を作動し、集光器５２からレーザー光線ＬＢを照射する。レーザー光線ＬＢが照射される領域は、図５（ａ）に示すように、上記した照射領域工程において設定された照射領域１２２ａであり、第一の音響光学偏向手段５４、及び第二の音響光学偏向手段５５に印加される電圧を適宜制御することにより、レーザー光線ＬＢのスポットＳＰ（φ５０μｍ）が、照射領域１２２ａ内において一箇所に偏ることなく、均一に分散して位置付けられる。そして、レーザー光線ＬＢが繰り返し照射領域１２２ａに照射されて、図５（ａ）のＡ−Ａ断面として示されている図５（ｂ）から理解されるように、裏面１０ｂ側から細孔１６（φ４５０μｍ）が形成される。 Here, in order to form pores reaching the electrode pad 12a of the desired device 12 from the back surface 10b side of the substrate 10, the device 12 for starting laser processing and the electrode pad 12a are determined. Then, the moving means 30 is operated to move the chuck table 28, and based on the coordinate position information of the electrode pad 12a stored in the control means 100, the position corresponding to the electrode pad 12a forming the pore is moved to It is positioned directly below the condenser 52 of the laser beam irradiation means 50. From the state where the electrode pad 12a is positioned immediately below the condenser 52 in this way, the X-axis moving means 31 is operated to start the machining feed in the X-axis direction at a predetermined speed, and the condenser 52 is irradiated. A state in which it is determined whether or not there is an irradiation area 122a set corresponding to the electrode pad 12a in the irradiation possible range of the laser beam LB, and it is judged that the irradiation area 122a is included in the irradiation range of the laser beam LB. Then, the laser beam irradiation means 50 is operated, and the laser beam LB is emitted from the condenser 52. The area irradiated with the laser beam LB is, as shown in FIG. 5A, the irradiation area 122a set in the irradiation area step described above, and includes the first acousto-optical deflection unit 54 and the second acousto-optical deflection. By appropriately controlling the voltage applied to the means 55, the spot SP (φ50 μm) of the laser beam LB is uniformly distributed and positioned without being concentrated in one place in the irradiation region 122a. Then, the laser beam LB is repeatedly irradiated to the irradiation region 122a, and as can be understood from FIG. 5B shown as the AA cross section of FIG. 5A, the pores 16 (φ450 μm are formed from the back surface 10b side. ) Is formed.
なお、上記レーザー光線照射工程におけるレーザー加工条件は、以下のように設定される。
レーザー光線の波長 ：３４３ｎｍ
繰り返し周波数 ：４０ｋＨｚ
平均出力 ：２Ｗ
パルス幅 ：１０ｐｓ
スポット径 ：５０μｍ
The laser processing conditions in the laser beam irradiation step are set as follows.
Laser beam wavelength: 343nm
Repetition frequency: 40 kHz
Average output: 2W
Pulse width: 10 ps
Spot diameter: 50 μm
（検出工程）
上記したレーザー光線照射工程が実施されると共に、基板１０を構成するリチウムタンタレートから発せられる第一のプラズマ光と、電極パッド１２ａから発せられる第二のプラズマ光とを検出する検出工程を実施する。該検出工程について、以下に説明する。
(Detection process)
The laser beam irradiation step described above is performed, and the detection step of detecting the first plasma light emitted from the lithium tantalate forming the substrate 10 and the second plasma light emitted from the electrode pad 12a is performed. The detection step will be described below.
検出工程では、上述したレーザー光線照射工程を実施している状態において、制御手段１００に対し、プラズマ検出手段７０の第一のホトデテクター７４、及び第二のホトデテクター７５から光強度信号が電圧値で出力される。図６には、第一プラズマ光の光強度を検出する第一のホトデテクター７４から出力される電圧値Ｖ（ＬＴ）と、第二のプラズマ光の光強度を検出する第二のホトデテクター７７から出力される電圧値Ｖ（Ｃｕ）とが、時間経過とともに示されている。図６において横軸は時間（Ｔ）を示し、縦軸は光強度に相当する電圧値（Ｖ）を示している。 In the detection step, in the state where the above laser beam irradiation step is performed, the light intensity signal is output as a voltage value from the first photodetector 74 and the second photodetector 75 of the plasma detection means 70 to the control means 100. It In FIG. 6, the voltage value V (LT) output from the first photodetector 74 that detects the light intensity of the first plasma light and the output from the second photodetector 77 that detects the light intensity of the second plasma light. The voltage value V (Cu) to be applied is shown over time. In FIG. 6, the horizontal axis represents time (T) and the vertical axis represents voltage value (V) corresponding to light intensity.
図６に示すように、基板１０の裏面１０ｂから上記した照射領域１２２ａに対するレーザー光線ＬＢの照射を開始すると、基板１０にレーザー光線ＬＢが照射されることで第一のプラズマ光が発生し、第一のホトデテクター５４から出力される電圧値Ｖ（ＬＴ）が上昇し始め、所定の電圧値（例えば２．５Ｖ）に到達し、レーザー光線ＬＢが電極パッド１２ａに到達するまでは、略一定の値で推移する。その後、レーザー光線ＬＢが電極パッド１２ａに達することで、第一のホトデテクター７４によって出力される電圧値Ｖ（ＬＴ）が下降し始める。 As shown in FIG. 6, when the irradiation of the laser beam LB from the back surface 10b of the substrate 10 to the irradiation region 122a is started, the substrate 10 is irradiated with the laser beam LB to generate the first plasma light, and the first plasma light is generated. The voltage value V (LT) output from the photodetector 54 starts to rise, reaches a predetermined voltage value (for example, 2.5V), and changes at a substantially constant value until the laser beam LB reaches the electrode pad 12a. . Then, when the laser beam LB reaches the electrode pad 12a, the voltage value V (LT) output by the first photodetector 74 starts to drop.
（レーザー照射終了工程）
上記した検出工程によれば、第一のプラズマ光と、第二のプラズマ光の発生状態を検出することができる。この検出工程において第二のプラズマ光を検出することにより、レーザー光線ＬＢの照射を停止するレーザー照射終了工程を実施する。該レーザー照射終了工程について、より具体的に説明する。
(Laser irradiation end process)
According to the detection process described above, the generation states of the first plasma light and the second plasma light can be detected. By detecting the second plasma light in this detecting step, the laser irradiation ending step of stopping the irradiation of the laser beam LB is carried out. The laser irradiation termination step will be described more specifically.
レーザー光線ＬＢが電極パッド１２ａに達した場合、図６に示すように、第二のホトデテクター７５によって出力される電圧値Ｖ（Ｃｕ）が上昇し始める。しかし、上昇直後は、細孔１６が電極パッド１２ａに対して照射領域１２２ａ全域で充分に貫通したとはいえず、細孔１６に導電性部材を埋設しても導通不良を起こすおそれがある。これに対処すべく、本実施形態では、細孔１６が電極パッド１２ａに対して充分な領域で達したことを検出するため、図６に示すように、第二のホトデテクター７５から出力される電圧値Ｖ（Ｃｕ）に対する閾値Ｓ(例えば、１．０Ｖ）が設定されている。第二のホトデテクター７５から出力される電圧値Ｖ（Ｃｕ）と、この閾値Ｓとを比較して、電圧値Ｖ（Ｃｕ）が閾値Ｓを上回ったことが判定されたならば、細孔１６が電極パッド１２ａに充分な領域で達して適正な細孔１６が形成されたと判断し、制御手段１００によって、レーザー光線照射手段５０に指示信号を出し、レーザー光線ＬＢの照射を終了させる。なお、閾値Ｓによる上記判定を行わず、レーザー光線照射工程をそのまま継続して実施すると、点線で示すように、電圧値Ｖ（Ｃｕ）’はさらに上昇し、略一定の電圧値(例えば、２．５Ｖ）で推移する状態となる。しかし、ここまで上昇させてしまうと、電極パッド１２ａに貫通孔が開いてしまう恐れがあるため、閾値Ｓはこれよりも低い値に設定される。 When the laser beam LB reaches the electrode pad 12a, the voltage value V (Cu) output by the second photodetector 75 starts to rise, as shown in FIG. However, immediately after the ascent, it cannot be said that the pores 16 have sufficiently penetrated the electrode pad 12a in the entire irradiation region 122a, and even if a conductive member is embedded in the pores 16, there is a possibility that conduction failure will occur. In order to deal with this, in the present embodiment, in order to detect that the pores 16 have reached the electrode pad 12a in a sufficient area, the voltage output from the second photodetector 75 as shown in FIG. A threshold value S (for example, 1.0 V) for the value V (Cu) is set. If the voltage value V (Cu) output from the second photodetector 75 is compared with this threshold value S and it is determined that the voltage value V (Cu) exceeds the threshold value S, the pores 16 are It is judged that the proper pores 16 have been formed by reaching the electrode pad 12a in a sufficient area, and the control means 100 issues an instruction signal to the laser beam irradiation means 50 to terminate the irradiation of the laser beam LB. If the laser beam irradiation step is continued without performing the above determination based on the threshold value S, the voltage value V (Cu) ′ is further increased as indicated by the dotted line, and a substantially constant voltage value (for example, 2. It will be in a state of transition at 5 V). However, if it is raised to this level, the through hole may open in the electrode pad 12a, so the threshold value S is set to a value lower than this.
上記したように、レーザー光線照射工程、検出工程、及びレーザー照射終了工程を、Ｘ軸送り手段３１によってチャックテーブル２８をＸ軸方向に加工送りしながら実施し、一の電極パッド１２ａに対応して電極パッド１２ａに達する適正な細孔１６が形成されたならば、Ｘ軸方向で隣接する隣の電極パッド１２ａが集光器５２の直下のレーザー光線ＬＢの照射領域に位置付けられたか否かを判定し、上記と同様のレーザー光線照射工程、検出工程、及びレーザー照射終了工程を実施する。これを繰り返すことにより、Ｘ軸方向に配列された全ての電極パッド１２ａに対して細孔１６を形成する。Ｘ軸方向に配列された全ての電極パッド１２ａに対応する細孔１６を形成したならば、Ｙ軸移動手段３２を作動して、基板１０をＹ軸方向に割り出し送りして、Ｙ軸方向で隣接する電極パッド１２ａの列に対して、上記したのと同様の一連のレーザー加工を実施する。これらを繰り返すことにより、基板１０上に形成された全ての電極パッド１２ａに対応する適正な細孔１６を形成することができる。 As described above, the laser beam irradiation step, the detection step, and the laser irradiation end step are performed while the chuck table 28 is processed and fed in the X-axis direction by the X-axis feed means 31, and the electrode corresponding to one electrode pad 12a is formed. When the proper pores 16 reaching the pad 12a are formed, it is determined whether or not the adjacent electrode pad 12a adjacent in the X-axis direction is positioned in the irradiation region of the laser beam LB immediately below the condenser 52, The same laser beam irradiation step, detection step, and laser irradiation end step as described above are performed. By repeating this, the pores 16 are formed in all the electrode pads 12a arranged in the X-axis direction. When the pores 16 corresponding to all the electrode pads 12a arranged in the X-axis direction are formed, the Y-axis moving means 32 is operated to index and feed the substrate 10 in the Y-axis direction, A series of laser processing similar to that described above is performed on the row of adjacent electrode pads 12a. By repeating these steps, it is possible to form appropriate pores 16 corresponding to all the electrode pads 12a formed on the substrate 10.
上記したように、本実施形態では、照射領域設定工程により、電極パッド１２ａの大きさを検出し、形成される細孔１６が電極パッド１２ａの内側に位置するようにレーザー光線ＬＢの照射領域１２２ａを設定している。これにより、電極パッド１２ａに細孔１６が至った際に、レーザー光線ＬＢが確実に電極パッド１２ａに照射され、第二のプラズマ光を充分に検出することができ、電極パッド１２ａに穴を開けることなく、適正な細孔１６を形成することができる。なお、照射領域設定工程において、照射領域１２２ａを設定する際に、電極パッド１２ａに内接する円１２１の面積に対し、照射領域１２２ａの面積が９５％以下となるように照射領域を設定することが好ましい。この照射領域１２２ａの設定条件の根拠について以下のように説明する。 As described above, in the present embodiment, in the irradiation area setting step, the size of the electrode pad 12a is detected, and the irradiation area 122a of the laser beam LB is set so that the pores 16 to be formed are located inside the electrode pad 12a. It is set. With this, when the pores 16 reach the electrode pad 12a, the laser beam LB is surely applied to the electrode pad 12a, the second plasma light can be sufficiently detected, and a hole can be opened in the electrode pad 12a. Therefore, proper pores 16 can be formed. In the irradiation area setting step, when setting the irradiation area 122a, the irradiation area may be set so that the area of the irradiation area 122a is 95% or less of the area of the circle 121 inscribed in the electrode pad 12a. preferable. The basis of the setting conditions of the irradiation area 122a will be described as follows.
本発明の発明者らは、電極パッド１２ａに対応して基板１０の裏面１０ｂからレーザー光線ＬＢを照射して適正な細孔１６を形成するための好適な照射領域１２２ａの面積について検討すべく、以下のような実験を行った。なお、下記の各実験において変更したパラメータ以外の加工条件は、上記した本実施形態の加工条件に沿って設定しており、以下の説明ではその余の加工条件に関する説明は省略している。 The inventors of the present invention consider the area of a suitable irradiation region 122a for forming the proper pores 16 by irradiating the laser beam LB from the back surface 10b of the substrate 10 corresponding to the electrode pad 12a. Experiments such as The processing conditions other than the parameters changed in the following experiments are set according to the processing conditions of the present embodiment described above, and the description of the remaining processing conditions is omitted in the following description.
＜実験１＞
電極パッド１２ａに内接する円(直径５００μｍ）の面積に対し、照射領域１２２ａを構成する円の面積が略１１０％になるように直径５２４μｍの円の照射領域を設定し、上記した実施形態と同条件で細孔１６を形成した。その結果、電極パッド１２ａには貫通孔が開いてしまった。
<Experiment 1>
The irradiation area of the circle having a diameter of 524 μm is set so that the area of the circle forming the irradiation area 122a is approximately 110% of the area of the circle (diameter 500 μm) inscribed in the electrode pad 12a. The pores 16 were formed under the conditions. As a result, a through hole was opened in the electrode pad 12a.
＜実験２＞
電極パッド１２ａに内接する円(直径５００μｍ）の面積に対し、照射領域１２２ａを構成する円の面積が略１００％になるように直径５００μｍの円の照射領域を設定し、上記した実施形態と同条件で細孔１６を形成した。その結果、電極パッド１２ａには実験１と比較して小さいが、貫通孔が開いてしまった。
<Experiment 2>
With respect to the area of the circle (diameter 500 μm) inscribed in the electrode pad 12a, the irradiation area of the circle having a diameter of 500 μm is set so that the area of the circle forming the irradiation area 122a is approximately 100%. The pores 16 were formed under the conditions. As a result, a through hole was opened in the electrode pad 12a although it was smaller than in Experiment 1.
＜実験３＞
電極パッド１２ａに内接する円(直径５００μｍ）の面積に対し、照射領域１２２ａを構成する円の面積が略９６％になるように直径４９０μｍの円の照射領域を設定し、上記した実施形態と同条件で細孔１６を形成した。その結果、電極パッド１２ａには窪みは見られたものの、貫通孔は開かなかった。
<Experiment 3>
The circular irradiation area having a diameter of 490 μm is set so that the area of the circle forming the irradiation area 122a is approximately 96% of the area of the circle (diameter 500 μm) inscribed in the electrode pad 12a. The pores 16 were formed under the conditions. As a result, the electrode pad 12a had a depression, but the through hole was not opened.
上記した実験結果から、本発明者らは、第二のプラズマ光を検出して、電極パッド１２ａに穴を開けることなく適正な細孔１６を形成するためには、照射領域設定工程において照射領域１２２ａを設定する際に、電極パッド１２ａに内接する内接円１２１の面積よりも照射領域１２２ａを規定する円の面積を小さくすればよいこと、特に、照射領域１２２ａの面積が、該内接円１２１に対して９５％以下であることが好ましいことを見出した。これにより、第二のプラズマ光を充分に検出することができ、電極パッド１２ａに穴を開けることなく、適正な細孔１６を形成することができる。 From the above experimental results, the present inventors have found that in order to detect the second plasma light and form the proper pores 16 without making holes in the electrode pad 12a, the irradiation region setting step is performed. When the area 122a is set, the area of the circle defining the irradiation area 122a may be smaller than the area of the inscribed circle 121 inscribed in the electrode pad 12a, and in particular, the area of the irradiation area 122a is the inscribed circle. It was found that it is preferably 95% or less with respect to 121. As a result, the second plasma light can be sufficiently detected, and proper pores 16 can be formed without making a hole in the electrode pad 12a.
上記した実施形態では、基板１０をリチウムタンタレートにより構成した例を示したが、本発明はこれらに限定されない。基板１０をシリコン、リチウムナイオベート（ＬＮ）、ガラス等、他の部材により構成することもできる。その場合は、基板１０として採用する物質に応じて第一のプラズマ光の波長も変化するため、これに対応すべく第一のバンドパスフィルター７３によって通過させる波長域を調整する。なお、電極パッド１２ａとしては銅が採用されることが一般的であるが、本発明は他の部材(例えば金等）により構成することを除外しない。その場合は、上記した第一のバンドパスフィルター７３と同様に、採用する金属に応じて第二のバンドパスフィルター７６によって通過させる波長を調整するとよい。 In the above-described embodiment, an example in which the substrate 10 is made of lithium tantalate has been shown, but the present invention is not limited to these. The substrate 10 can also be made of other members such as silicon, lithium niobate (LN), and glass. In that case, the wavelength of the first plasma light also changes depending on the substance used as the substrate 10, so that the wavelength band to be passed by the first bandpass filter 73 is adjusted to accommodate this. Although copper is generally used for the electrode pad 12a, the present invention does not exclude that the electrode pad 12a is made of another member (such as gold). In that case, similarly to the first bandpass filter 73 described above, the wavelength passed by the second bandpass filter 76 may be adjusted according to the metal used.
１：レーザー加工装置
１０：基板
１２：デバイス
１２ａ：電極パッド
１２１：内接円
１２２ａ：照射領域
１４：分割予定ライン
１６：細孔
２０：保持手段
２１：Ｘ軸方向可動板
２２：Ｙ軸方向可動板
２４：支柱
２６：カバー板
２８：チャックテーブル
３０：移動手段
４０：吸着チャック
４２：クランプ
５０：レーザー光線照射手段
５２：集光器
５４：第一の音響光学偏向手段
５５：第二の音響光学偏向手段
６０：撮像手段
７０：プラズマ検出手段
７１：プラズマ光受光手段
７２ａ：第一の光路
７２ｂ：第二の光路
７３：第一のバンドパスフィルター
７４：第一のホトデテクター
７６：第二のバンドパスフィルター
７７：第二のホトデテクター
１００：制御手段
1: Laser processing device 10: Substrate 12: Device 12a: Electrode pad 121: Inscribed circle 122a: Irradiation area 14: Divided line 16: Pore 20: Holding means 21: X-axis direction movable plate 22: Y-axis direction movable Plate 24: Post 26: Cover plate 28: Chuck table 30: Moving means 40: Adsorption chuck 42: Clamp 50: Laser beam irradiating means 52: Concentrator 54: First acousto-optical deflecting means 55: Second acousto-optical deflecting Means 60: Imaging means 70: Plasma detection means 71: Plasma light receiving means 72a: First optical path 72b: Second optical path 73: First bandpass filter 74: First photodetector 76: Second bandpass filter 77: Second photo detector 100: Control means
Claims (2)
電極パッドに対応する裏面からレーザー光線を照射するレーザー光線照射工程と、
レーザー光線の照射によって基板に細孔が形成されると共に基板から発せられる第一のプラズマ光と電極パッドから発せられる第二のプラズマ光とを検出する検出工程と、
該検出工程において、該第二のプラズマ光を検出した際、レーザー光線の照射を停止するレーザー照射終了工程と、
を少なくとも含み、
該レーザー光線照射工程の前に、該電極パッドの大きさを検出し、形成される細孔が該電極パッドの内側に位置するようにレーザー光線の照射領域を設定する照射領域設定工程が実施されるレーザー加工方法。 A laser processing method for forming pores reaching a electrode pad by irradiating a laser beam on the back surface of a substrate on the surface of which a device having an electrode pad is formed,
A laser beam irradiation step of irradiating a laser beam from the back surface corresponding to the electrode pad,
A detection step of detecting the first plasma light emitted from the substrate and the second plasma light emitted from the electrode pad together with the formation of pores in the substrate by the irradiation of the laser beam,
In the detecting step, when the second plasma light is detected, a laser irradiation ending step of stopping irradiation of a laser beam,
Including at least
Before the laser beam irradiation step, an irradiation area setting step is performed in which the size of the electrode pad is detected and the irradiation area of the laser beam is set so that the pores formed are located inside the electrode pad. Processing method.
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| Application Number | Priority Date | Filing Date | Title |
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| JP2018199132A JP2020066015A (en) | 2018-10-23 | 2018-10-23 | Laser processing method |
| US16/600,739 US10985060B2 (en) | 2018-10-23 | 2019-10-14 | Laser processing method using plasma light detection for forming a pore in a substrate |
| ATA50906/2019A AT521999A2 (en) | 2018-10-23 | 2019-10-22 | Laser processing |
| DE102019216320.3A DE102019216320A1 (en) | 2018-10-23 | 2019-10-23 | LASER PROCESSING METHOD |
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| Publication number | Publication date |
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| US10985060B2 (en) | 2021-04-20 |
| DE102019216320A1 (en) | 2020-04-23 |
| US20200126856A1 (en) | 2020-04-23 |
| AT521999A2 (en) | 2020-07-15 |
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